The baby was so small and the tumour so big, it was a very difficult job.

Dr Ayman Eissa

The huge growth was crushing Isabel’s throat, stopping her breathing.

Doctors raced against time to fit a tube in a ground-breaking procedure before the baby stopped getting oxygen from mum Maureen, 35.

Dr Ayman Eissa said: “The relief when I secured the tube was unimaginable. It was definitely the most stressful few minutes of my career.”

The tumour, which weighed a sixth of Isabel’s 3lb 9oz weight, was removed 10 days later and medics expect Isabel to make a full recovery.

Doctors at Sheffield Children’s Hospital and Jessops Maternity Hospital noticed the abnormal growth during a scan at 33 weeks. Isabel and twin sister Alexandra were delivered by Caesarean section and doctors started the race to fit a tube.

Dr Eissa said: “The placenta will continue to supply oxygen for up to five minutes, but you can never be sure, it could break off at any time.

“The baby was so small and the tumour so big, it was a very difficult job.”

The Children’s Hospital believes that Isabel, now 16 weeks old and back home in Hoyland, South Yorks, is the first twin baby to undergo the rare procedure in the UK.